diff --git a/base/etc/one-context.d/02-ssh_public_key b/base/etc/one-context.d/02-ssh_public_key
index cb83b2d..2057636 100755
--- a/base/etc/one-context.d/02-ssh_public_key
+++ b/base/etc/one-context.d/02-ssh_public_key
@@ -16,18 +16,24 @@
 # limitations under the License.                                             #
 #--------------------------------------------------------------------------- #
 
+function add_keys {
+    while read key; do
+        if ! grep -q -F "$key" /root/.ssh/authorized_keys; then
+            echo "$key" >> /root/.ssh/authorized_keys
+        fi
+    done
+}
+
 [ -z "${SSH_PUBLIC_KEY}${EC2_PUBLIC_KEY}" ] && exit 0
 
 mkdir -m0700 -p /root/.ssh
 
-echo -n '' > /root/.ssh/authorized_keys
-
 if [ -n "$SSH_PUBLIC_KEY" ]; then
-    echo "$SSH_PUBLIC_KEY" >> /root/.ssh/authorized_keys
+    echo "$SSH_PUBLIC_KEY" | add_keys
 fi
 
 if [ -n "$EC2_PUBLIC_KEY" ]; then
-    echo "$EC2_PUBLIC_KEY" >> /root/.ssh/authorized_keys
+    echo "$EC2_PUBLIC_KEY" | add_keys
 fi
 
 chmod 600 /root/.ssh/authorized_keys